The present invention relates to a flow generating apparatus such as an air blower or pump for supplying fluid and also relates to a method of manufacturing the apparatus.
There is known a disc type flow generating apparatus in which a plurality of annular flow generating plates are arranged in directions perpendicular to a rotational axis thereof and adapted to be rotated about the rotational axis, and in which fluid is fed due to a frictional force caused between surfaces of these flow generating plates and the fluid, as disclosed in Japanese Patent Publication No. 58-17359 (17359/1983), for example.
The flow generating apparatus of this known type has a simple structure, thus being advantageous in its manufacturing cost, but involves a problem of inadequate performance with respect to the flow rate.
An induction motor has been usually utilized for driving a flow generating apparatus. Since the maximum rotational speed of the induction motor is generally determined on the basis of the power source frequency, a maximum value of the rotational speed of the flow generating apparatus is limited. Such limitation of the rotational speed also depends upon the durability of the shaft bearings used, for example. Such limitation of the maximum rotational speed necessitates an improvement of a space efficiency of the flow generating apparatus, i.e. increasing the flow rate with the same size of the apparatus, instead of increasing the rotational speed in a case where a greater flow rate is needed.